+589 Boris is playing on the mall escalators. One escalator goes up, one goes down, and one is out of service; otherwise, they're all identical. The up and down escalators go at the same speed. You can assume that Boris always runs at the same speed.
Boris can run up the up escalator in 6 seconds. He can run up the down escalator in 30 seconds. How many seconds does it take him to run up the out-of-service escalator?
+36916 d / ( r + e ) = 6 d / ( r- e ) = 30 e = escalator speed r = run speed
30 r - 30 e = d
6r + 6e = d or 6e = d - 6r <====== multiply by -5 and sub into top equation
d = 30r-5d + 30 r
6d = 60 r
60 / 6 = d/r = 10 seconds Varaax is correct ......I fell prey to my warning about time in distance calcs !
+36916 This is kinda like the boat and current speed questions
(6 + 30)/ 2 = speed on still escalator = 18 seconds
+36916 d / ( r + e ) = 6 d / ( r- e ) = 30 e = escalator speed r = run speed
30 r - 30 e = d
6r + 6e = d or 6e = d - 6r <====== multiply by -5 and sub into top equation
d = 30r-5d + 30 r
6d = 60 r
60 / 6 = d/r = 10 seconds Varaax is correct ......I fell prey to my warning about time in distance calcs !
+36916 Redux for posterity....figured a simpler way while sleeping last night
RATES Rate WITH escaltor 1 escalator / 6 sec Rate against escalator 1 escalator / 30 seconds
NOW it is like the airplane/windspeed or boat/ current speed calcualtions
rate on still escalator = ( 1/6 + 1/30 ) / 2 = (6/30) /2 = 6/60 = 1 /10 = rate on still esc ( 1 esc / 10 sec)
then time on still escalator = 10 sec
+36916 I had my COVID vaccine this morning and have been breathing paint fumes the rest of the day.....that's what I'm gonna use for an excuse !!!!! Haha
thanx Varxaax !
+118608 Gee you two got in quick!
I know none of my friends in Germany have theirs yet. Not even the first one.
And very few in Australia have it. Our supply of vaccine has been partially blocked by Italy.
Which is not all that unreasonable. Europeans need it far more than we do.
Life is almost normal here in Australia.
+128408 We have a large supply.......what we DON'T have is a high vaccination rate.......some people are still balking at getting the vaccine.......go figure !!!!
+118608 Yea well, if half the population gets inoculated it might be enough to protect the other half as well.
It will certainly cut down on infection rates anyway, so the hospitals will have more chance of coping.
I will get inoculated when I am told to but I don't care how long away that is.
I hope our government starts demanding people are inoculated before they return, or visit Australia. I know that is being looked at.
+2094 The vaccine has not been approved for kids yet, so unfortunately 12-year-old Cal will not be getting the vaccine anytime soon.
